Method for disrupting an electrochemical generator

Abstract

The invention relates to a method for breaking up an electrochemical generator (10), the electrochemical generator (10) comprising a negative electrode (20) containing lithium or sodium and a positive electrode (30), the method comprising the step of breaking up the electrochemical generator (10) in an ionic liquid solution (100) containing an ionic liquid and a so-called oxidizing redox substance, the so-called oxidizing redox substance being able to be reduced at the negative electrode (20), thereby discharging the electrochemical generator (100).

Description

Technical Field

[0001] The present invention relates to a method for the disruption of electrochemical generators, such as Li-ion, Na-ion or lithium metal accumulators or batteries, in particular with a view to their recovery and / or storage.

[0002] More specifically, the invention relates to a method for disrupting an electrochemical generator in a solution comprising an ionic liquid and a redox-active substance. The redox-active substance is used to discharge the electrochemical generator. The ionic liquid allows this step to be carried out in complete safety, in particular by preventing the formation of an explosive atmosphere.

[0003] The recyclable parts of the electrochemical generator can then be safely recycled. Background Art

[0004] An electrochemical generator is a device that converts chemical energy into electrical energy. For example, it can be a battery cell or a storage battery.

[0005] The market for batteries, especially for lithium batteries of the Li-ion type, is currently expanding rapidly, on the one hand because of so-called portable applications (smartphones, computers, cameras, etc.) and on the other hand because of new mobility-related applications (electric vehicles and hybrid vehicles) and so-called stationary applications (connection to the power grid).

[0006] Due to the growth in the number of batteries in recent years, the issue of recycling batteries has become a major challenge.

[0007] Generally speaking, a lithium-ion battery includes an anode, a cathode, a separator, an electrolyte, and a casing.

[0008] Typically, the anode is formed of graphite mixed with a PVDF-type binder deposited on copper foil, while the cathode is a lithium metal intercalation material (such as LiCoO2, LiMnO2, LiNiO2, Li3NiMnCoO6 or LiFePO4) mixed with a binder and deposited on aluminum foil.

[0009] The electrolyte is a mixture of a non-aqueous solvent and a lithium salt and optionally an additive to slow down secondary reactions.

[0010] It operates as follows: During charging, lithium is extracted from the metal oxide and intercalated into graphite, where it is thermodynamically unstable. During discharge, the process is reversed and lithium ions are intercalated into the lithium metal oxide.

[0011] As batteries are used, aging causes them to lose capacity and they must be recycled.

[0012] However, a large number of batteries or battery packs to be recycled are still at least partially charged and their fragmentation produces sparks and significant ignition or even explosion, especially in the case of primary lithium cells (Li-SOCl2).

[0013] Damaged batteries must also be recycled. However, these batteries can have lithium metal deposits on the anode that are highly reactive when exposed to air or water.

[0014] Therefore, scrapped and / or damaged batteries that are to be recycled must be handled with extreme care.

[0015] The battery recycling method includes multiple steps:

[0016] - including the dismantling phase and the pre-processing steps to ensure safety,

[0017] - Thermal and / or hydrometallurgical treatments to recover the various materials and convertible metals contained in these cells and accumulators.

[0018] To date, the main difficulty has been in the stage of making these lithium-based (primary and secondary) electrochemical systems safe.

[0019] More specifically, when a seal failure occurs, the electrolyte - a toxic, flammable and corrosive product - leaks out in liquid and gaseous form. The vapors thus generated and mixed with air can form an explosive atmosphere (ATEX). This atmosphere can ignite when it comes into contact with an ignition source (such as a spark) or a hot surface. This can lead to an explosion, producing thermal and pressure effects. In addition, electrolyte salts such as lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium perchlorate LiClO4 and lithium hexafluoroarsenate LiAsF6 release particularly toxic and corrosive fumes containing phosphorus, fluorine and / or lithium. For example, hydrofluoric acid (HF) can be formed during the thermal decomposition of Li-ion batteries.

[0020] To overcome these disadvantages, the battery can be crushed in a chamber with a controlled atmosphere and a controlled pressure. For example, document WO 2005 / 101564 A1 describes a method for recovering lithium anode batteries by hydrometallurgical means at ambient temperature and in an inert atmosphere. The atmosphere contains argon and / or carbon dioxide. These two gases will exhaust oxygen and form a protective gas space above the crushed charge. The presence of carbon dioxide will cause lithium metal passivation by forming lithium carbonate on the surface, which slows down the reactivity of this metal. The hydrolysis of the lithium-containing crushed charge leads to the formation of hydrogen. In order to prevent any risk of hydrogen ignition and explosion, the lithium-containing crushed charge is added to the aqueous solution in a carefully controlled manner, and a very strong turbulence is generated above the bath. This operation is associated with the consumption of oxygen in the atmosphere. The water becomes rich in lithium hydroxide, and then lithium is recovered by adding sodium carbonate or phosphoric acid.

[0021] In the method described in patent US 5,888,463, a cryogenic method is used to make cells and accumulators safe. Before being crushed, the cells and accumulators are frozen in liquid nitrogen at -196°C. The crushed material is then immersed in water. To prevent any formation of H2S, the pH is maintained at a pH of at least 10 by adding LiOH. The lithium salts formed (Li2SO4, LiCl) are precipitated as carbonates by adding sodium carbonate.

[0022] Document CA 2 313 173 A1 describes a method for recycling lithium-ion battery cells. The battery cells are previously cut open in an anhydrous inert atmosphere. A first organic solvent (acetonitrile) is used to dissolve the electrolyte, and a second organic solvent (NMP) is used to dissolve the binder. The particle embedding material is then separated from the solution and reduced by electrolysis.

[0023] In document WO 2011 / 113860 A1, the so-called dry technology is described. The temperature of the mill is maintained between 40°C and 50°C and the mixture of hydrogen and oxygen released from the battery is eliminated by cyclonic air movement to minimize the risk of fire. The battery fragments and dust recovered after screening are cooled to ambient temperature. The extraction of lithium appears to be carried out by reaction with oxygen and moisture in the air, resulting in risks associated with the simultaneous presence of hydrogen, oxygen and heat, leading to combustion and explosion. In addition, the electrolyte is decomposed, resulting in risks, losses and difficulties in managing dust and gases.

[0024] The UmiCore VAL'EAS described in the article by Georgi-Maschler et al. ("Development of a recycling process for Li-ion batteries", Journal of Power Sources 207 (2012) 173-182) TM The method combines pyrometallurgical and hydrometallurgical treatments. The disassembled batteries are fed directly into a furnace. Pyrometallurgical treatment is used to passivate them: the electrolyte evaporates at around 300°C; the plastic is pyrolyzed at 700°C, while the remaining part is finally melted and reduced at 1200°C-1450°C. In this method, some organic materials contained in the battery cells act as reducing agents. Aluminum and lithium are lost. Iron, copper and manganese are recovered in an aqueous solution. Cobalt and nickel are recovered as LiCoO2 and Ni(OH)2 and recycled to form cathode materials. However, this type of thermal treatment consumes a lot of energy and leads to significant decomposition of the battery components.

[0025] Document EP 0 613 198 A1 describes a method for recovering materials from lithium battery cells. The battery cells are cut open either under a high-pressure water jet or in an inert atmosphere to prevent fire. The lithium then reacts with water, alcohol or acid to form lithium hydroxide, lithium alkoxide or lithium salt (e.g. LiCl), respectively. However, the use of high-pressure water jet cutting to ensure process safety consumes a large amount of water and generates H2 gas in the air.

[0026] To date, the various methods described above require high temperature processing, low temperature processing and / or processing in a controlled atmosphere, which are conditions that are difficult to industrialize and / or costly. Summary of the invention

[0027] It is an object of the present invention to provide a method which overcomes the disadvantages of the prior art, in particular a method for fragmenting electrochemical generators which can be easily industrialized without requiring high temperatures, very low temperatures and / or a controlled atmosphere.

[0028] This is achieved by a method for disrupting an electrochemical generator comprising a positive electrode and a negative electrode comprising lithium or sodium, the method comprising the step of disrupting the electrochemical generator in an ionic liquid solution comprising an ionic liquid and a so-called oxidizing redox substance, the so-called oxidizing redox substance being able to be reduced at the negative electrode, thereby discharging the electrochemical generator.

[0029] The present invention is fundamentally different from the prior art in that the electrochemical generator is fragmented in the presence of an ionic liquid solution comprising an ionic liquid and a redox species.

[0030] The disruption method opens the battery and enables access to the lithium or sodium. The ionic liquid solution safely opens the electrochemical generator and allows the introduction of reactive redox species that discharge the electrochemical generator by redoxing with the lithium (or the sodium) (which is performed simultaneously with the disruption of the electrochemical generator).

[0031] The absence of water prevents the generation of hydrogen, oxygen and / or heat, which could create an explosive atmosphere.

[0032] In the following description, when lithium is described, this lithium may be replaced by sodium.

[0033] According to a first example, in the case of a lithium metal battery, the reduction reaction of the so-called oxidizing redox substance leads to the oxidation of the lithium metal in ionic form.

[0034] According to another example, in the case of lithium-ion batteries, the reduction reaction of the so-called reduced redox species leads to the deintercalation of the lithium ions from the active material of the negative electrode.

[0035] The free ions extracted from the anode migrate through the ion-conducting electrolyte and are fixed at the cathode, where they form thermodynamically stable lithium oxide. Thermodynamically stable is understood to mean that the oxide does not react violently with water and / or air.

[0036] With the crushing method according to the invention, the lithium is extracted quickly from the negative electrode (anode) while preventing any risk of ignition and / or explosion.

[0037] Advantageously, the solution contains a second so-called reducing redox species which can be oxidized at the positive electrode, the so-called oxidizing redox species and the so-called reducing redox species forming a redox species pair.

[0038] A redox pair, also called a redox mediator, an electrochemical shuttle or a redox shuttle, is understood to mean an oxidation / reduction (Ox / Red) pair in solution, wherein the oxidant can be reduced at the anode (negative electrode) and the reductant can be oxidized at the cathode (positive electrode). The redox pair generates a redox reaction, thereby discharging the generator, so that the mediator remains intact and no reagent is consumed.

[0039] One or more redox species allow the electrochemical generator to be significantly or even completely discharged, while reducing the chemical energy of the electrodes, thereby reducing the potential difference between the electrodes (anode and cathode). This discharge also reduces internal short circuit effects.

[0040] The method is cost-effective because the redox couple in solution simultaneously produces the redox reaction at the electrodes of the electrochemical generator, resulting in zero reagent consumption; the solution can be used to sequentially make multiple electrochemical generators safe.

[0041] Advantageously, the redox species pair is a metal pair, which is preferably selected from Mn 2+ / Mn 3+ 、Co 2+ / Co 3+ Cr 2+ / Cr 3 + Cr 3+ / Cr 6+ 、V 2+ / V 3+ 、V 4+ / V 5+ Sn 2+ / Sn 4+ 、Ag + / Ag 2+ , Cu + / Cu2+ 、Ru 4+ / Ru 8+ or Fe 2+ / Fe 3+ , organic molecular pairs, metallocene pairs such as Fc / Fc + , or halogenated molecules such as Cl2 / Cl - or Cl - / Cl 3- .

[0042] Advantageously, the ionic liquid solution comprises an additional ionic liquid.

[0043] Advantageously, the ionic liquid solution forms a deep eutectic solvent.

[0044] Advantageously, the electrochemical generator is immersed in the ionic liquid solution.

[0045] Advantageously, the electrochemical generator is discharged at a temperature in the range of 0°C to 100°C, preferably 15°C to 60°C.

[0046] Advantageously, the electrochemical generator is discharged in air.

[0047] Advantageously, before the step of discharging the electrochemical generator, the method comprises a disassembly step and / or a sorting step.

[0048] Advantageously, after the step of discharging the electrochemical generator, the method comprises a pyrometallurgical and / or hydrometallurgical step.

[0049] The crushing method according to the invention has many advantages:

[0050] - enabling the generator to be safe (discharged) and switched on in a single step, which saves a lot of time and investment,

[0051] - No wet crushing step is performed, which avoids the problems associated with managing hydrogen, oxygen and heat and thus explosive atmospheres (safety, handling of effluents, additional economic costs), and avoids the use of large amounts of water and the need to treat aqueous effluents;

[0052] - no thermal treatment processes are carried out, which avoids the problems associated with gas emissions (such as greenhouse gases or any other gas harmful and dangerous to humans and the environment), in particular as regards their disposal, and reduces the financial and energy costs of the process;

[0053] - The restrictions associated with the use of water are greatly reduced, since ionic liquids are non-volatile, non-flammable and chemically stable at temperatures that can exceed 200° C. (eg, between 200° C. and 400° C.);

[0054] - when opening the cell, in particular with an inert gas, no control of the gas atmosphere is required, which simplifies the process and makes it more cost-effective,

[0055] - the lithium can be directly accessed, which ensures that the generator is discharged very quickly, compared to prior art methods where the discharge step requires several hours or even days,

[0056] - Use of a single redox species: No redox pairs need to be used, which broadens the choice and properties of available species, since the species only needs to have a higher electrochemical potential than lithium, which is the species with the lowest electrochemical potential. Therefore, the lithium can be extracted by any species that can be reduced to a potential greater than -3.05 V relative to the SHE.

[0057] - Damaged generators, undischarged or insufficiently discharged generators and / or generators that cannot be discharged (because their terminals are degraded and / or corroded) are handled when opened without causing safety problems.

[0058] Any reliance on the damaged state of the generator is prevented by breaking it open. Using breaking in a water-free and air-free environment overcomes this type of problem.

[0059] - when opening the cell, in particular with an inert gas, no control of the gas atmosphere is required, which simplifies the process and makes it more cost-effective,

[0060] -Quick and easy to implement.

[0061] Other characteristics and advantages of the present invention will appear from reading the additional description given below.

[0062] It goes without saying that these additional descriptions are provided only for the purpose of illustrating the present invention and shall not be interpreted as constituting limitations on the present invention in any way. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be better understood after reading the following description of exemplary embodiments, which are given for illustrative purposes only and are not intended to limit the scope of the present invention, with reference to the accompanying drawings, in which:

[0064] Figure 1 A cross-sectional view schematically shows an electrochemical generator according to a specific embodiment of the present invention,

[0065] Figure 2 A cross-sectional view of an electrochemical generator is schematically shown according to a specific embodiment of the method of the present invention.

[0066] To make the drawings easier to read, the different parts shown in the figures are not necessarily shown to a uniform scale.

[0067] The different possibilities (alternatives and embodiments) must be understood as not excluding one another and can be combined with one another. DETAILED DESCRIPTION

[0068] In the following, even if the description relates to lithium-ion batteries, the invention can be transferred to any electrochemical generator, for example to a battery comprising a plurality of batteries (also called battery packs) connected in series or in parallel depending on the nominal operating voltage and / or the amount of energy to be supplied, or to a battery cell.

[0069] These various electrochemical devices may be of metal ion (eg, lithium ion or sodium ion) type, or of Li metal type, and the like.

[0070] It can also be a primary system such as Li / MnO2, or a redox flow battery.

[0071] Advantageously, an electrochemical generator is selected whose potential is greater than 1.5 V.

[0072] First reference Figure 1 , which shows a lithium ion (or Li-ion) battery 10. A single electrochemical cell is shown, however the generator may include a plurality of electrochemical cells, each cell including a first electrode 20 (in this case an anode) and a second electrode 30 (in this case a cathode), a separator 40, and an electrolyte 50. According to another embodiment, the first electrode 20 and the second electrode 30 may be reversed.

[0073] The anode (negative electrode) 20 is preferably carbon-based, for example, made of graphite that can be mixed with a PVDF-type binder and deposited on a copper foil. It can also be a lithium mixed oxide such as lithium titanate Li4Ti5O for Li-ion batteries. 12 (LTO) or sodium mixed oxides such as sodium titanate for Na-ion batteries. It can also be a lithium alloy or a sodium alloy, depending on the chosen technology.

[0074] The cathode (positive electrode) 30 is a lithium ion intercalation material for a Li-ion battery. It can be a layered oxide of the LiMO2 type, a LiMPO4 phosphate having an olivine structure, or a LiMn2O4 spinel compound. M represents a transition metal. For example, a positive electrode made of LiCoO2, LiMnO2, LiNiO2, Li3NiMnCoO6 or LiFePO4 is selected.

[0075] The cathode (positive electrode) 30 is a sodium ion intercalation material for a Na ion battery. It can be a sodium oxide type material containing at least one transition metal element, a sodium phosphate or sodium sulfate type material containing at least one transition metal element, a sodium fluoride type material, or a sulfide type material containing at least one transition metal element.

[0076] The embedding material can be mixed with a polyvinylidene fluoride type binder and deposited on the aluminum foil.

[0077] The electrolyte 50 comprises a lithium salt (e.g., LiPF6, LiBF4, LiClO4) or a sodium salt (e.g., N3Na) depending on the selected battery technology dissolved in a non-aqueous solvent mixture. The solvent mixture is, for example, a binary or ternary mixture. The solvent is, for example, selected from cyclic carbonate-based solvents (ethylene carbonate, propylene carbonate, butylene carbonate), linear or branched carbonate-based solvents (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane) in different proportions.

[0078] Alternatively, it can also be a polymer electrolyte comprising a polymer matrix made of organic and / or inorganic material, a liquid mixture comprising one or more metal salts, and optionally a mechanical reinforcement material. The polymer matrix can comprise one or more polymer materials, for example selected from polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), or poly(ionic liquids) of the poly(N-vinylimidazolium)bis(trifluoromethylsulfonylimide) type, N,N-diethyl-N-(2-methoxyethyl)-N-methylammoniumbis(trifluoromethylsulfonyl)imide (DEMM-TFSI).

[0079] The cell may be wound around itself about a winding axis, or have a stacked structure.

[0080] A housing 60, such as a polymer bag or a metal package (eg made of steel), is used to seal the battery.

[0081] Each electrode 20, 30 is connected to a current collector 21, 31, which passes through the housing 60 and forms terminals 22, 32 (also called output terminals or electrical terminals or electrodes) outside the housing 60, respectively. The current collectors 21, 31 have two functions: to provide mechanical support for the active material and to provide electrical conduction for the terminals of the battery. The terminals (also called electrical terminals or electrodes) form the output terminals and are intended to be connected to a "power receiver".

[0082] According to some configurations, one of the terminals 22, 32 (e.g., the terminal connected to the negative pole) can be connected to the ground of the electrochemical generator. Hereinafter, the ground is referred to as the negative potential of the electrochemical generator, while the positive terminal is the positive potential of the electrochemical generator. Thus, the positive potential is defined as the positive pole / terminal and all metal parts connected by electrical continuity from that pole.

[0083] Intermediate electronics may optionally be arranged between the terminal connected to the grounding device and the grounding device.

[0084] The electrochemical generator is disrupted in the presence of an ionic liquid solution 100 (also referred to as a solution of ionic liquid) containing an ionic liquid and a redox species capable of reacting with lithium to neutralize lithium in order to make the electrochemical generator safe.

[0085] This ionic liquid solution 100 simultaneously prevents contact between waste (cell or battery) / water / air and ensures that the waste is discharged through the electrochemical redox species present in the ionic liquid. Therefore, the entire process is safe with respect to the fire triangle.

[0086] Preferably, the electrochemical generator 10 is completely discharged. The free ions are fixed in the cathode 30, where they form a thermodynamically stable lithium metal oxide that does not react violently with water or air. This is done at a low environmental and economic cost. In addition, the treatment does not hinder recycling (in particular, the electrolyte does not decompose). The discharge time will be estimated according to the type of battery cell and battery and the charging rate.

[0087] The electrochemical generator 10 is at least partially covered by the ionic liquid solution. Preferably, it is completely immersed in the ionic liquid solution 100 ( Figure 2 ).

[0088] The ionic liquid solution 100 comprises at least one ionic liquid LI1 , referred to as solvent ionic liquid, and a redox-active substance A.

[0089] An ionic liquid is understood to mean an association of at least one cation and one anion which gives rise to a liquid having a melting temperature of less than or approximately 100° C. These are molten salts.

[0090] Solvent ionic liquids are understood to mean ionic liquids which are thermally and electrochemically stable so as to minimize decomposition of the medium during discharge phenomena.

[0091] The ionic liquid solution may also contain one or more (eg two or three) additional ionic liquids, ie the ionic liquid solution contains a mixture of several ionic liquids.

[0092] Additional ionic liquids (denoted as LI2) are understood to mean ionic liquids that enhance one or more properties with respect to ensuring safety and discharge procedures. Specifically, this may relate to one or more of the following properties: extinction, flame retardancy, redox shuttle, salt stabilizer, viscosity, solubility, hydrophobicity and conductivity.

[0093] Advantageously, the ionic liquid and optional additional ionic liquid are liquid at ambient temperature (20°C to 25°C).

[0094] For the solvent ionic liquid and for the one or more additional ionic liquids, the cation is preferably selected from the group consisting of: imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium.

[0095] Advantageously, it is preferred to select cations that have a broad cation window that is large enough to observe cathode reactions that prevent or minimize decomposition of the ionic liquid.

[0096] Advantageously, LI1 and LI2 will have the same cation to increase the solubility of LI2 in LI1. In many possible systems, a medium with low cost, low environmental impact (biodegradability) and non-toxicity is preferred.

[0097] Advantageously, the anion is used to simultaneously provide a wide electrochemical window, moderate viscosity, low melting temperature (liquid at ambient temperature), and good solubility with the ionic liquid and other species in solution, without causing hydrolysis (decomposition) of the ionic liquid.

[0098] An example of such an anion is the TFSI anion, which satisfies the various association criteria described above, such as LI1: [BMIM][TFSI], or using an ionic liquid of the type [P66614][TFSI], an ionic liquid 1-ethyl-2,3-trimethyleneimidazolium bis(trifluoromethanesulfonyl)imide ([ETMIm][TFSI]), an ionic liquid N,N-diethyl-N-methyl-N-2-methoxyethylammonium bis(trifluoromethylsulfonyl)amide [DEME][TFSA], an ionic liquid N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PYR14][TFSI]), or an ionic liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI). The anion can also be of the bis(fluorosulfonyl)imide (FSA or FSI) type, such as the ionic liquid N-methyl-N-propylpyrrolidinium FSI (P13-FSI), N-methyl-N-propylpiperidinium FSI (PP13-FSI), or 1-ethyl-3-methylimidazolium FSI (EMI-FSI), etc.

[0099] The anions of the solvent ionic liquid LI1 and / or the additional liquid LI2 may be complexing anions to form a complex with the electrochemical shuttle.

[0100] Other associations with ionic liquids are also possible, in which the cation is associated with an anion which may be organic or inorganic and preferably has a wide anodic window.

[0101] The ionic liquid solution 100 advantageously forms a deep eutectic solvent (or DES). This is a liquid mixture at ambient temperature obtained by forming a eutectic mixture of two salts, with the general formula:

[0102] [Cat] + .[X] - .z[Y]

[0103] in:

[0104] [Cat] + is the cation of the solvent ionic liquid (e.g. ammonium),

[0105] [X] - Is a halogen anion (such as C1 - ),

[0106] [Y] is X that can react with the solvent ionic liquid - Anion-complexed Lewis or Bronsted acids, and

[0107] z is the number of molecules Y.

[0108] According to the properties of Y, eutectics can be divided into three types.

[0109] The first type corresponds to type I eutectic:

[0110] Y=MCl x , where, for example, M = Fe, Zn, Sn, Fe, Al, Ga.

[0111] The first type corresponds to type II eutectic:

[0112] Y=MClx.yH2O, where, for example, M=Cr, Co, Cu, Ni, Fe.

[0113] The first type corresponds to the type III eutectic:

[0114] Y=RZ, where, for example, Z=CONH2, COOH, OH.

[0115] For example, DES is choline chloride associated with a very low toxic H-bond donor such as glycerol or urea, which ensures that DES is non-toxic and very low cost.

[0116] According to another exemplary embodiment, choline chloride can be replaced by betaine.Although these systems have a limited electrochemical stability window, they can guarantee flooding and deactivation of the battery, which is optionally opened.

[0117] Advantageously, a compound "Y" is selected that can act as an electrochemical shuttle, which can be oxidized and / or reduced. For example, Y is a metal salt that can be dissolved in an ionic liquid solution to form a metal ion. For example, Y comprises iron.

[0118] For example, a eutectic can be formed between a chloride anion ionic liquid and metal salts FeCl2 and FeCl3 having different ratios and different cations.

[0119] This type of reaction can also be carried out with a Type II eutectic which binds water molecules to the metal salt; this does not pose a hazard when the water content is low. Low is typically understood to mean less than 10 wt% of the solution, for example 5 to 10 wt% of the solution.

[0120] Type III eutectics can also be used with mixtures of the [LI1] / [Y] type, where the ionic liquid and a hydrogen bond donor substance (Y) are combined, where LI1 can be a quaternary ammonium and Y can be a complexing molecule (hydrogen bond donor) such as urea, ethylene glycol or thiourea.

[0121] It is also possible to prepare mixtures that will advantageously modify the properties of the solution used to discharge the medium. In particular, solvent ionic liquids of the [BMIM][NTF2] type can be combined, which are very stable and liquid at ambient temperature, but which dissolve electrochemical shuttles (or redox mediators), such as ferric chloride, to a small extent.

[0122] For example, an additional ionic liquid LI2 of the [BMIM][Cl] type can be combined, which will enhance the solubility of the metal salt in chloride form by complexing with the anion of LI2. This allows both good transport properties and good solubility of the redox mediator, thus enhancing the discharge phenomenon.

[0123] Solution 100 contains a redox species. It is an ion or a species in solution that can be oxidized at the negative electrode according to A→A*, where A* is the oxidized form of substance A ( Figure 2 ). Redox species make the battery safe by extracting lithium from the negative electrode.

[0124] The proposed method renders the battery unreactive to air.

[0125] Electrochemical couples or combinations thereof may also be used. Preferably, it is a redox couple that acts as an electrochemical shuttle (or redox mediator) by performing a redox reaction to reduce decomposition of the mediator.

[0126] Redox correspondence is understood to mean oxidizing agents and reducing agents in solution that can be reduced and oxidized, respectively, at the electrodes of the cell. Its oxidation / reduction can advantageously allow the regeneration of redox species that were initially present in solution. The use of an electrochemical shuttle allows the device to be operated in a closed loop and reduces the decomposition of the medium.

[0127] The oxidizing agent and the reducing agent may be introduced in equimolar or unequal molar ratios.

[0128] One of the redox substances may originate from the generator itself. It may in particular be cobalt, nickel and / or manganese.

[0129] The redox couple can be an electrochemical metal pair or a combination thereof: Mn 2+ / Mn 3+ 、Co 2+ / Co 3+ Cr 2+ / Cr 3+ Cr 3+ / Cr 6+ 、V2 + / V 3+ 、V 4+ / V 5+ Sn 2+ / Sn 4+ 、Ag + / Ag 2+ , Cu + / Cu 2+ 、Ru 4+ / Ru 8+ or Fe 2+ / Fe 3+ .

[0130] The redox species and redox pairs may also be selected from organic molecules, in particular from: 2,4,6-tri-tert-butylphenoxy, nitroxynitroxide / 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), tetracyanoethylene, tetramethylphenylenediamine, dihydrophenazines, for example aromatic molecules with methoxy groups, such as anisole, N,N-dimethylamino groups of dimethoxybenzene, or N,N-dimethylaniline groups such as N,N-dimethylaminobenzene. Other examples include 10-methyl-phenothiazine (MPT), 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB) and 2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborolane (PFPTFBDB).

[0131] This can also come from the metallocene family (Fc / Fc+, Fe(bpy)3(ClO4)2 and Fe(phen)3(ClO4)2 and their derivatives) or from the halogenated family (Cl2 / Cl - , Cl- / Cl 3- Br2 / Br - , I2 / I - ,I - / I3 - ).

[0132] In particular, a bromide or chloride is selected. Preferably, it is a chloride that can easily complex the metal. For example, iron complexed with chloride ions forms FeCl4 - , FeCl4 - This will reduce the reactivity of the negative electrode.

[0133] It may also be tetramethylphenylenediamine.

[0134] It is also possible to combine a plurality of redox pairs, in which the metals of the metal ions are identical or different.

[0135] For example, select Fe 2+ / Fe 3+ and / or Cu + / Cu 2+ The latter dissolves in both oxidation states, is non-toxic, and does not decompose the ionic liquid.

[0136] The solution may contain a fire extinguishing agent and / or a flame retardant to prevent thermal runaway, especially in the event of opening the battery. It may be an alkyl phosphate, optionally fluorinated (fluorinated alkyl phosphate), such as trimethyl phosphate, triethyl phosphate, or tris(2,2,2-trifluoroethyl)phosphate. The concentration of the active substance may be 80 wt% to 5 wt%, preferably 30 wt% to 10 wt%.

[0137] Optionally, the ionic liquid solution may contain a desiccant, and / or an agent to enhance material transport, and / or a protective agent as a stabilizer / reducer of corrosive and toxic substances, for example selected from PF5, HF and POF3.

[0138] Agents that enhance material transfer are, for example, part of a co-solvent that can be added to reduce viscosity.

[0139] It can be a small proportion of water, such as 5% water.

[0140] Preferably, an organic solvent is selected for effective action without generating emission or flammability risks. It may be vinylene carbonate (VC), gamma-butyrolactone (γ-BL), propylene carbonate (PC), poly(ethylene glycol) or dimethyl ether. The concentration of the agent for enhancing material transport is advantageously 1 wt% to 40 wt%, more advantageously 10 wt% to 40 wt%.

[0141] Protective agents capable of reducing and / or stabilizing corrosive and / or toxic elements are, for example, compounds of the butylamine type, carbodiimides (of the N,N-dicyclohexylcarbodiimide type), N,N-diethylaminotrimethylsilane, tris(2,2,2-trifluoroethyl)phosphite (TTFP), amino compounds (such as 1-methyl-2-pyrrolidone), fluorinated carbamates or hexamethylphosphoramide. It may also be a compound of the cyclophosphazene family, such as hexamethoxycyclotriphosphazene.

[0142] Advantageously, the ionic liquid solution comprises less than 10 wt% water, preferably less than 5 wt% water.

[0143] Even more preferably, the ionic liquid solution is free of water.

[0144] The process may be carried out at a temperature of 0°C to 100°C, preferably 20°C to 60°C, even more preferably the process is carried out at ambient temperature (20°C-25°C).

[0145] The method can be carried out in air or in an inert atmosphere (such as argon, carbon dioxide, nitrogen or a mixture thereof), or in an atmosphere with a controlled oxygen content.

[0146] Where the electrochemical generator is immersed in an ionic solution, the solution may be stirred to improve reagent uptake. For example, this may involve stirring at a speed between 50 and 2000 rpm, preferably between 200 and 800 rpm.

[0147] For example, the crushing step is performed in a recycling process, and the recycling process may include the following steps: sorting, disassembling, crushing, and then recovering the elements to be recovered (for example, through pyrometallurgy, hydrometallurgy, etc.).

[0148] Safely open the generator to access its recyclable parts.

[0149] Illustrative and non-limiting examples of embodiments:

[0150] In this example, the discharge occurs in a glycerol-based medium (a mixture of choline chloride and glycerol).

[0151] The ionic liquid solution is an ionic liquid mixture comprising choline chloride and glycerol, the volume ratio of choline chloride to glycerol is 1:2 and the Cp is 2.2 Jg -1 .K -1 , the ionic liquid mixture has 5wt% trimethyl phosphate as a fire extinguishing agent. After the solution dries, the crushing area of ​​the sealed knife mill is filled with the solution. Then a 18650Li ion type battery cell is injected into the mill at room temperature. The rotation speed is 50rpm. The crushing process simultaneously opens the battery cell and allows the reaction between the lithium and the bath to occur, thereby discharging the battery cell and making the battery cell safe.

Claims

1. A method for breaking up an electrochemical generator (10), the electrochemical generator (10) comprising a positive electrode (30) and a negative electrode (20) comprising lithium or sodium, the method comprising the step of breaking up the electrochemical generator (10) in an ionic liquid solution (100) comprising an ionic liquid and a so-called oxidizing redox substance, the so-called oxidizing redox substance being able to be reduced at the negative electrode (20), thereby discharging the electrochemical generator (10), the ionic liquid comprising at least one cation and one anion producing a liquid having a melting temperature of less than or equal to 100° C.

2. The method according to claim 1, wherein the ionic liquid solution (100) contains a second so-called reducing redox species capable of being oxidized at the positive electrode (30), the so-called oxidizing redox species and the so-called reducing redox species forming a redox species pair.

3. The method according to claim 1, wherein the redox species pair is a metal pair, an organic molecule pair, a metallocene pair or a halogenated molecule pair.

4. The method according to claim 3, wherein the redox species pair is selected from Mn 2+ / Mn 3+ 、Co 2+ / Co 3+ Cr 2+ / Cr 3+ Cr 3+ / Cr 6+ 、V 2+ / V 3+ 、V 4+ / V 5+ Sn 2+ / Sn 4+ 、Ag + / Ag 2+ , Cu + / Cu 2+ 、Ru 4+ / Ru 8+ or Fe 2+ / Fe 3+ .

5. The method according to claim 3, wherein the redox species pair is Fc / Fc + .

6. The method according to claim 3, wherein the redox species pair is Cl2 / Cl - or Cl - / Cl 3- .

7. The method according to any one of claims 1 to 6, wherein the ionic liquid solution (100) comprises an additional ionic liquid.

8. The method according to any one of claims 1 to 6, wherein the ionic liquid solution (100) forms a deep eutectic solvent.

9. The method according to any one of claims 1 to 6, wherein the electrochemical generator (10) is broken up in an inert atmosphere.

10. The method according to any one of claims 1 to 6, wherein before the step of crushing the electrochemical generator (10), the method comprises a disassembly step or a sorting step.

11. The method according to any one of claims 1 to 6, wherein after the step of fragmenting the electrochemical generator (10), the method comprises a pyrometallurgical or hydrometallurgical step.

12. The method according to any one of claims 1 to 6, wherein the electrochemical generator (10) is a lithium ion generator or a sodium ion generator.

13. The process according to any one of claims 1 to 6, wherein the process is carried out at a temperature ranging from 0°C to 100°C.

14. The method according to any one of claims 1 to 6, wherein the cation of the ionic liquid is selected from the group consisting of imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium.

15. The method according to any one of claims 1 to 6, wherein the anion of the ionic liquid is selected from the group consisting of bis(trifluoromethylsulfonyl)imide TFSI, bis(trifluoromethylsulfonyl)amide TFSA, bis(fluorosulfonyl)imide FSI and halogen anions.

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